void get_nxt(){
	nxt[0]=0;
	nxt[1]=0;
	int i=2;
	while ( i<=n ){
		int t = nxt[i-1];
		while ( t!=0 && text2[t+1]!=text2[i] ) t=nxt[t];
		if ( text2[t+1]==text2[i] ) nxt[i] = t+1; else nxt[i]=0;
		i++;
	}
}

bool check(){
	int i=1, t=1;
	while ( i<=n*2 ){
		while ( t<=n && wh[i]==text2[t] ){i++;t++;}
		if ( t>n ){
			//for (int i=1;i<=2*n;++i) printf("%d ",wh[i]);printf("\n");
			return true;
			}
		if ( t==1 ) i++;
		t = nxt[t-1]+1;
	}
	return false;
}
